Developments have been carried out on various types of nonvolatile semiconductor memory devices having a bit cost scalable (BiCS) structure in recent years. A three-dimensional BiCS structure achieves an increase in a memory capacity with lower costs.
A nonvolatile semiconductor memory device having the BiCS structure is produced by processing a stacked layer body at one operation. The number of bits can be increased as the layered number is increased. For this reason, the BiCS structure can decrease costs per bit.
On the other hand, a poly-crystalline semiconductor is used for a channel region in the nonvolatile semiconductor memory device using the BiCS structure. The structure mentioned above entails a problem that electron mobility is low in the channel.